A bare blank that I was sanding and didn't notice the warp at first. I will try bending the opposite way and appling heat...……..
As best as I can tell, with bending balsa wood it's mostly the elevated temperature that does the job, but some moisture helps a bit, and and does a
lot to conduct heat into the interior of the wood. So if you're bending it dry, take a
good long time to get it warmed up. If I'm un-warping a profile fuselage I may spend five minutes or more playing a heat gun over the back half of the fuselage, trying to warm the wood without blistering the paint.
Personally, if it's in the bare wood stage I think I'd at least spritz it with water, to generate steam that'll conduct heat to the interior and to (hopefully) loosen up the top layer of fibers a bit.
One of these days I'm going to make me a full-on steam bending fixture. Eventually. Before I die. Maybe. Or I'll just direct in my will that I be buried in a steam-bent coffin.